Natural Chemical May Treat Strokes

June 24, 2002 -- A naturally occurring chemical that stimulates nerve growth may one day help stroke patients recover. Testing in humans could begin early next year for inosine, which appears to help the brain "rewire" itself after injury.

If those trials prove successful, inosine could represent a major advance over existing treatments, researchers say, because it can be given up to 24 hours after a stroke. Current therapies must be given within two to three hours, and fewer than 10% of stroke patients are treated during this window.

In newly reported studies involving rats, inosine was shown to promote the growth of nerve cells in areas of the brain that remained undamaged following stroke. This new nerve growth, in turn, took over some of the functions of the stroke-damaged parts of the brain. The findings are reported in the June 25 issue of the Proceedings of the National Academy of Sciences.

"At least in principle, we have shown that inosine can greatly stimulate the rewiring of the brain," says lead investigator Larry I. Benowitz, PhD, of Harvard Medical School. "In stroke there is a loss of brain circuitry. If we can prompt compensatory growth from the remaining intact nerve fibers, that could be very beneficial."

Benowitz and colleagues injected inosine into the brains of rats with experimentally induced strokes. Following recovery, the treated rats showed dramatic improvement in physical performance over rats given placebo treatments.

In one experiment, the animals were trained to reach through the bars of a cage to get food pellets placed just outside. By the fourth week of the study, half of the inosine-treated rats used their stroke-affected paws to reach for food, while none of the placebo treated rats did.

"This is a totally novel approach to treatment that suggests we can repair the brain after injury," says National Stroke Association spokesman Lawrence Brass, MD. "This is one of the first studies to provide evidence that this can happen, that it can happen in mammals, and that it can happen in a way that translates into behavioral improvement." Brass is a professor of neurology at Yale University School of Medicine.